The present invention relates to a method and relevant apparatus for blowing oxygen into, for instance, L.D. converters (Linz Donawitz converters) in unstationary manners or by varying the delivery of oxygen into the converter.
The reaction rates theoretically obtainable between carbon and oxygen in the present physical conditions of L. D. converters, are substantially higher than those obtained in practice.
Certain reaction of the refining process takes place less quickly than possible because of the relatively little amount of interaction between the various layers of material in the converter. This is particularly true of the reactions of desulphoration, dephosphoration, oxidation of manganese, and formation of the slag because of relatively little interaction between the slag and the underlying material.
The deficiency in the reactions between slag and underlying materials results in the difficulty of producing in L.D. converters, steels with higher qualitative characteristics and the reduction of these deficiencies will obtain from the same converters higher quality steels with high specific deliveries, that is, with higher yield.
As the coefficients of mass transportation are sufficiently high even for the metal-slag reactions, the limitation to the interaction between the steps present, and consequently to the reaction rates, consists in the reduced exchange surfaces between said steps. The limited exchange surfaces are caused by that through the present blowing manners the drawing of the slag in the bath, and in general the beginning of the contact between the steps, are entrusted only and exclusively to the partial turbulence of the oxygen jets and to the consequent phenomena of instability present in the oxygen-bath interface.
The partial turbulence of the oxygen jets opening into the passage conduits through the slag layer, is useful as on the lateral surfaces of said conduits is exerted an action of drawing for the slag by said jets. Besides, this fact justifies the increase in the number of the nozzles in the blowings with high deliveries, for the consequent increase in the lateral surfaces of the conduits.
Further, the turbulence of the oxygen jets originates phenomena of unstability on the surface of the impression on the bath, said instability being sufficient for the oxygen mixing in the other steps.
The phenomena described originate the dispersion of the various components of the burden which, being the system essentially constituted by a fluid matrix, tend to separate under the action of the gravity field; said separation is balanced by the arrival of new amounts of components in form of liquid or gaseous particles, owing to the action of the oxygen jets.
As said mixing is associated to instability phenomena, though present also at the oxygen-slag interface, it occurs for fair amounts of the system components, that is in a discontinuous way. It results that, in order to improve the mixing and consequently the interaction of the various steps, it is advisable to favor a discontinuous series of phenomena.
In order to increase the instability phenomena present in the slag and bath, or to originate them when they are not yet present, it is possible to act on the feeding of the oxygen phase, making it discontinuous or particularly giving it a pulsating feature.